External fixation frames may be used to correct skeletal deformities. The Ilizarov external fixation devices, for example, are widely used for this purpose. The Ilizarov-type devices may be used to translate bone segments by manipulating rings connected to each bone segment and a plurality of threaded rods connected to the manipulation rings.
A bone fragment can be moved, in general, from its original position as in a nonunion or malunion or from its intended position as in congenital deformities along six separate axes, a combination of three orthogonal translational axes (e.g., typical “X,” “Y” and “Z” axes) and three orthogonal rotational axes (e.g., rotation about such typical “X,” “Y” and “Z” axes). This movement generally occurs via manipulation of one or more adjustable length struts connected at each end thereof to rings of the external fixation device.
External fixation devices are generally attached to the boney skeleton, such as the femur or tibia, for example, with threaded and/or smooth pins and/or threaded and/or smooth and/or beaded wires. Such constructs are commonly referred to as orthopedic external fixators or external skeletal fixators. External fixators may be utilized to treat acute fractures of the skeleton, soft tissue injuries, delayed union of the skeleton when bones are slow to heal, nonunion of the skeleton when bones have not healed, malunion whereby broken or fractures bones have healed in a malposition, congenital deformities whereby bones develop a malposition, and bone lengthening, widening, or twisting.
Examples of external fixation devices include those described in U.S. Pat. No. 8,333,766 and U.S. Patent Publication No. 2014/0058389, the disclosures of which are both hereby incorporated by reference herein. After a bone is fixed to such an external fixation device, one bone fragment may be moved in any combination of the six degrees of freedom relative to a fixed bone fragment. The movement is generally directed by a preoperative and/or postoperative plan defining precise movement of rings and/or struts to result in precise movement of one bone fragment relative to a fixed bone fragment.